As a maintenance supervisor, you get to lead your team through installing equipment and repairing that equipment. With that being said, we're sure you gathered that this isn't a entry-level career. You're going to need some experience in doing the work as well as experience as a leader to excel past other applicants.
The majority of your day will be spent in an office, as it's your job to coordinate projects and assign workers to job sites. But sometimes you'll need to go out and inspect those job sites to ensure the project isn't running behind.
On the topic of making sure the project isn't running behind...you'll also need to check the equipment and make sure no mistakes are being made. That's where your attention to detail skill will really come into play. It's important that your team satisfies the client entirely. It's never a bad thing to have a reoccuring customer.